How to Find the Key of Any Song by Ear

How to find the key of any song by ear.Using burritos.
"Can you taste it?"
I paused, burrito in hand, mouth open. Chris was fond of pulling pranks, but he hadn't messed with my food. Yet.
"Taste what?"
Chris started laughing "Don't worry, I didn't jizz in it or anything. I just put some curry powder in, just to see what it tasted like."
I took another bite of my burrito. There it was, an unmistakeable hint of curry. Like an ex-girlfriend at a party. It just shouldn't have been there.
"Don't quit your day job, Ramsey."
Chris had just confirmed what I had already known for a long time. Bass players are just the worst.
Chris taught me a valuable lesson that day Burritos taste weird with curry powder mixed in. When something is a little out in a burrito, you can taste it straight away, but only if you're used to the particular flavours of a well made burrito. The same idea applies to finding the key of a song You can find the key to any song, as long as you're used to the flavour.
This article will show you a method of finding the key of a song by using just the guitar. No humming the tonic like a moron, no guesswork, just a system that uses the pentatonic scale. Also, with this system, you'll be able to figure out the key of a song in 20 seconds or less.
Just a side note-this method is great for the more harmonically standard styles of music, like rock and pop and country, but it won't work over jazz or classical music. (BUMMER DUDE)
This method has two steps: Find all possible places where four fret spaces sound consonant on the high e string, and play position 1 of the pentatonic in each of those.

Four fret spaces

Four fret spaces is just a term for me to describe the first two notes of the pentatonic scale. If we're playing the A Minor Pentatonic scale, the notes on the high e string are 5 8, which have four frets contained in them (5, 6, 7, 8). Thus, we have four fret spaces.
When we don't know the key of a song, we'll use these four fret spaces to quickly identify potential candidates for the correct key.
If you look at the pentatonic scale in A Minor on a single string you get this:

If you look you can see two places that have these four fret spaces. Both of these four fret spaces have two notes, both which are consonant. See the diagram below.

Using this method we go from fumbling across the whole Fretboard looking for notes, to identifying two places on the high E string where these four fret spaces are consonant. Once we find these, we can decide which four fret space is pentatonic position one. We'll talk more about this later, but for now all you have to know is that in any key, there are only two four fret spaces (there are four in the above diagram, but 17 20 is an octave of 58, 12 15 is an octave of 03) on the high e string. Also, only one of them will sound right when you play position 1 using them.

Identify the four fret spaces

To find the spaces, play all the possible four fret spaces chromatically, and identify the two positions that are consonant. Do this by going chromatically up the Fretboard: 0 3, 1 4, 2 5, 3 6, etc. I'm just going to throw out a broad definition for consonant here they're notes that sound good. I'll cover this in more detail later.
(Note: you may find up to four of these four fret spaces initially, even without octaves. We'll weed out the incorrect spaces later).

Play position one of the pentatonic.

Let's continue with our original example. Let's say we've identified the following four fret spaces, 5 8 and 12 15. All you do now is play position one of the pentatonic in each of these spaces. They will sound very similar, but one will have the unmistakable flavour of the pentatonic and the other will sound a little off. Like a taste of curry powder where there shouldn't be.
Let's see what that would look like.

The red highlighted notes are the notes that will sound out of key. Play with these two positions with any backing track in A Minor (YouTube it). The highlighted red notes just don't sit right like the rest of the notes. The ability to quickly sense the notes that are incorrect is the essence of this technique.
Here's a full example of this method. Let's summarise this method before we begin:
1) Use the four fret spaces to locate the two places on the high e string where each note is consonant. Do this by chromatically by moving up the Fretboard: 0 3, 1 4, 2 5, 3 6 etc.
2) When you've located the two four fret spaces, play position one in each four fret space. They are only different by one note, as covered above. If you have trouble with this step you need to get used to the flavour of the pentatonic. (More on this later).
So, we're listening to a song, and we don't know what key it's in. Let's apply the method.
Step One: Play through all the four fret spaces on the high E string, listening out for the four fret spaces that are consonant*.
Go up chromatically from 03 to 11 14. When you find four fret spaces where both notes sound correct, write it down. You should end up with 2 ideally, but you may end up with 4. Let's say you end up with 5 8 and 12 15.
*What do I mean by consonant? I mean both notes sound like they are in key. If you play an F# in A Minor, it'll sound bad, or out of key. I'm generalising here, and in certain contexts that F# would sound great, BUT when you're playing the A Minor Pentatonic over an A Minor backing track, F# will sound BAD.
If you're unsure of whether you understand this concept, try soloing with any song for a few minutes, without using any scales. Can you hear when you play a bum note that's totally out of key? If you can, with practice this method will work well for you. If you can't hear the bum notes, there's help later on in this article.
Step Two: Play position one of the pentatonic on each of these four fret spaces.
Now you'll have to decide which one of these is the correct key. The more you are used to the flavour of the pentatonic, the easier this will be. They will sound similar, but only one will sound just like the pentatonic should. Note the still highlighted tell tale notes.

Once you've decided which of these pentatonic position 1 is, you've found the key of your song.
This is the best method I have found for teaching students to find the key of a song in a very short amount of time. Often this method can be well mastered after about two weeks.
I doubt all of you will find it that easy, so here are some common issues and solutions

Common difficulties:

I'm not sure which notes are consonant/correct/good!
If you're new to improvising this is common. The solution is to get used to the flavour of the pentatonic. Play with a backing track every day, using only position one of the pentatonic scale. It's hard to hit a wrong note with the pentatonic scale. Soon you'll hear any "out" notes as loud as a gunshot. A basic way to do this is if the track is in A Minor, play the A Minor Pentatonic. B Mino, B Minor Pentatonic etc. Find millions of backing tracks on YouTube by searching for "A Minor Backing Track" or any variations.

I can't identify the four fret space notes...
This is usually down to speeding through the 0 3, 1 4, 2 5, 3 6, process. Play all these notes quickly one after another and it all sounds like one big mush.
Think of the correct key of the song as a big old ball of jelly. When you hear notes that are out of key, the ball is stretched. After the ball is stretched you need to let the ball return to its original shape.
Translation: leave 2-5 seconds between each playing of the four fret space. This will allow the key to adjust back to its original "shape."

Should I use the high E string or the low E string?
You can use either, but I prefer the high E string. It is really clear whether the note is in or out.

I've identified the two four fret spaces, but I don't know which one is position one.
You're not used to the flavour of the pentatonic yet. Play with one backing track a day, using position one of the pentatonic. Play with backing tracks in A Minor, and really listen to the highlighted notes in the below diagram. Those are the notes that tell you you're in the wrong spot.
Like I talked about in the burrito example, you need to get used to the flavour of the classic burrito. It's only when you know the flavour of a classic burrito inside out that you can tell the difference between a classic burrito and a burrito that is just a little bit off.
It's the same with knowing the flavour of the pentatonic. You need to play the pentatonic with a backing track every day, so that when you're listening to the pentatonic in very similar positions you can just feel that flavour difference and you'll know which one is correct.

Action Steps:

1) Play with one backing track a day to get used to the flavour of the Pentatonic.
2) Attempt to identify the key of one song you like a day. Give yourself a maximum of two play throughs of the song. Write down your best guess.
3) Sign up for my free ear training course. This course will guide you through everything I talked about in this article in greater detail. The only goal of this course is to be able to identify the key of any song in seconds.
Let's face it, finding the key of any song is a huge part of any soloists ability. It just can't be covered in a series of articles, so I invite you to take part in the course here.
About The Author:
Hey guys, I'm Eoghan O'Neill and I'm a guitar teacher currently teaching in the West of Ireland, Galway to be precise! I'm starting a new blog, called "The Systematic Guitarist." It's a blog for intermediate and advanced guitar players interested in Soloing and Advanced Acoustic Guitar Playing. Check it out!

The 5 second method: listen for the tonic, hum the tonic, play a note on guitar that you think is close, identify the interval between the 2 notes, identify what you're tonic is based off the interval, you've now found the key, doesn't get any simpler. And for rock songs, assume its in E or A, 50% chance of getting it right.

so, which part of this was the "by ear" part? all I see is a trial-and-error approach, playing along to a song and searching for the right notes isn't really what I expected. I'm not saying that that approach is wrong, since I've basically done nothing else the last few years playing to songs, up to the point where I can "guess" the key of a song just be hearing with a rather high accuracy without even touching my guitar. But that's just overall experience, I guess. I've never needed any specific training.
"Let's face it, finding the key of any song is a huge part of any soloists ability." That's debatable. I've never jammed with anyone without knowing in which key we are playing, because that's always gonna be the first question before even starting.

The by ear part is exactly what you said - its a trial and error approach. Finding the key of a song is exactly that - testing the waters using a few notes, and then using your ear to identify the correct notes.
I disagree with your notion that you wouldn't need to find the key to a song as a soloist, but to each his own. I would prefer to have the skill, and I don't think anyone could argue that it isn't a good use of your time as a musician.
As for being able to hear the key of a song without even needing an instrument - I salute you sir, but I am sure you are in the minority of the musicians in the world who can just listen to a song say 'C Major'.

"I've never jammed with anyone without knowing in which key we are playing, because that's always gonna be the first question before even starting."
Well, you can do that, but only if everybody's musical hearing is good enough. When I play with a friend of mine, one of us just starts playing and the other one will figure out what the key is (or cheat by looking at what the other is playing on the fretboard).

You use the pentatonic scale to identify the key of the song - when you use the correct scale with a key - for example, the C Major pentatonic with a song in C Major, it has a very specific sound.
By getting used to that sound, you can quickly identify the key of any song,and the diagrams were there to try and help you see the method.

"bbbbuuttt.... what if I don't have perfect or relative pitch? or what if my ear got ran over by a truck before? c..c...c...could I still try going up and down the fretboard, looking for a pitch I can not recognize without any sort of problem?".
Even before I got into reading this article I had to stop, go down here, and write this comment down. It really pisses me off when someone in this world is absolutely CONVINCED at the fact that all human beings around the globe possesses the abilities of a friggin superman.
You do understand, my dear article writer (or at least the guy who wrote the title to this article) that there are alot more people in this world who can't find a correct pitch even if you tell them to go in a choromatical-diatonic ascend or descend with intervals until the find the correct pitch? they might hear it for a while, true, i'd give you that, but some of them will never be able to find that same pitch again unless you bring it up or play it to them, even when they'll try singing it back. That why we have ear training exercises for.
So I ask you dear writer, can anyone who is trying to recognize by themselves a pitch for a song while playing a guitar in the same time (assuming offcourse he is not superman and does not have a relative nor perfect pitch like most of the untrained ears around this world) recognize even a chord out of it?
Something to think about when you have students who doesn't have these kind of abilities or never bothered practicing them until you brought it up in one of their first ever guitar lessons.

Funnily enough this is how I used to find the key of a song. I can hear it now without a guitar but need the guitar to find the right specific note. Perhaps things haven't changed that much. I can look at the chords of a song and make an educated guess too, but you still have to listen to the song to be sure where the tonal center is.
The process doesn't apply to all pieces, like classical or jazz due to modulation being commonly employed in them. That said if you can identify the key changes, you can still use this process.

So, I have an honest question and am not looking to rail the author's method. Why the pentatonic scale for this? Is it just because of fewer notes and is therefore an easier scale to apply because of its universal nature? I don't really know the theory behind the pentatonic scale other than that it's five notes =/
When I try to find the key I tend to just use the major scale, and make diatonic patterns of the leading tone(7th note) to the tonic(1st note) and the median(3rd) to the subdominant(4th) or supertonic(2nd) to median for minor keys, as those note pairs(at least for major keys) are separated by a half step and that relationship seems to have the strongest pull to my ear.
That being said it's still hit and miss for me sometimes. I don't know the correct method for finding keys by ear, but that's my process. It seems basically the same. I just wondered why you chose the pentatonic instead? Ease of use? Less theory knowledge required? Perhaps I'm overthinking =|